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Abstract:

A catalyst for the metathesis of olefins in general and specifically for
the production of propylene from ethylene and butylene has been
developed. The catalyst comprises a tungsten metal compound, which
contains at least one tungsten-fluoro bond, dispersed or grafted onto a
support. A specific example of the catalyst is the compound
WOF(CH2CMe3)3 grafted onto a silica support.

Claims:

1. A catalyst for metathesis of olefins comprising a tungsten metal
compound characterized in that it contains at least one tungsten-fluorine
bond, the compound dispersed on a refractory oxide support wherein the
compound is chemically bonded to the support.

2. The catalyst of claim 1 where the tungsten containing compound is
selected from the group consisting of WR4F,
WOFR3,W(NR')FR3 and mixtures thereof and where "R" is an
organic group which does not have any hydrogen atoms beta to the
tungsten.

3. The catalyst of claim 2 where R is selected from the group consisting
of neopentyl (--CH2CMe3); methyl, 2,2-diethylpropyl
(--CH2C(CH2CH3)2Me), and 2,2-diethylbutyl
(--CH2C(CH2CH3)2CH2CH3).

4. The catalyst of claim 2 where R' is an organic group selected from the
group consisting of H, phenyl, 2,6-dimethylphenyl and methyl.

5. The catalyst of claim 1 where the tungsten-metal compound is present
in an amount from about 0.5 to about 10 wt-% of the catalyst as the
metal.

6. The catalyst of claim 1 where the refractory oxide support is selected
from the group consisting of silica, aluminas, silica-aluminas, titania,
zirconia and mixtures thereof.

7. The catalyst of claim 6 where the refractory oxide is silica.

8. The catalyst of claim 7 where the silica is an acid washed silica.

9. The catalyst of claim 1 where the refractory oxide support has a
surface area of at least 50 m2/g.

10. The catalyst of claim 9 where the refractory oxide support has a
surface area from about 80 to about 500 m2/g.

11-19. (canceled)

Description:

FIELD OF THE INVENTION

[0001] This invention relates to a catalyst for the metathesis of olefins
in general and specifically for the production of propylene from ethylene
and butylene.

DESCRIPTION OF RELATED ART

[0002] Propylene demand in the petrochemical industry has grown
substantially, largely due to its use as a precursor in the production of
polypropylene for packaging materials and other commercial products.
Other downstream uses of propylene include the manufacture of
acrylonitrile, acrylic acid, acrolein, propylene oxide and glycols,
plasticizer oxo alcohols, cumene, isopropyl alcohol, and acetone.
Currently, the majority of propylene is produced during the steam
cracking or pyrolysis of hydrocarbon feedstocks such as natural gas,
petroleum liquids, and carbonaceous materials (e.g., coal, recycled
plastics, and organic materials). The major product of steam cracking,
however, is generally ethylene and not propylene.

[0003] Steam cracking involves a very complex combination of reaction and
gas recovery systems. Feedstock is charged to a thermal cracking zone in
the presence of steam at effective conditions to produce a pyrolysis
reactor effluent gas mixture. The mixture is then stabilized and
separated into purified components through a sequence of cryogenic and
conventional fractionation steps. Generally, the product ethylene is
recovered as a low boiling fraction, such as an overhead stream, from an
ethylene/ethane splitter column requiring a large number of theoretical
stages due to the similar relative volatilities of the ethylene and
ethane being separated. Ethylene and propylene yields from steam cracking
and other processes may be improved using known methods for the
metathesis or disproportionation of C4 and heavier olefins, in
combination with a cracking step in the presence of a zeolitic catalyst,
as described, for example, in U.S. Pat. No. 5,026,935 and U.S. Pat. No.
5,026,936. The cracking of olefins in hydrocarbon feedstocks, to produce
these lighter olefins from C4 mixtures obtained in refineries and
steam cracking units, is described in U.S. Pat. No. 6,858,133; U.S. Pat.
No. 7,087,155; and U.S. Pat. No. 7,375,257.

[0004] Steam cracking, whether or not combined with conventional
metathesis and/or olefin cracking steps, does not yield sufficient
propylene to satisfy worldwide demand. Other significant sources of
propylene are therefore required. These sources include by-products of
fluid catalytic cracking (FCC) and resid fluid catalytic cracking (RFCC),
normally targeting gasoline production. FCC is described, for example, in
U.S. Pat. No. 4,288,688 and elsewhere. A mixed, olefinic C3/C4
by-product stream of FCC may be purified in propylene to polymer grade
specifications by the separation of C4 hydrocarbons, propane,
ethane, and other compounds.

[0005] Much of the current propylene production is therefore not "on
purpose," but as a by-product of ethylene and gasoline production. This
leads to difficulties in coupling propylene production capacity with its
demand in the marketplace. Moreover, much of the new steam cracking
capacity will be based on using ethane as a feedstock, which typically
produces only ethylene as a final product. Although some hydrocarbons
heavier than ethylene are present, they are generally not produced in
quantities sufficient to allow for their recovery in an economical
manner. In view of the current high growth rate of propylene demand, this
reduced quantity of co-produced propylene from steam cracking will only
serve to accelerate the increase in propylene demand and value in the
marketplace.

[0006] A dedicated route to light olefins including propylene is paraffin
dehydrogenation, as described in U.S. Pat. No. 3,978,150 and elsewhere.
However, the significant capital cost of a propane dehydrogenation plant
is normally justified only in cases of large-scale propylene production
units (e.g., typically 250,000 metric tons per year or more). The
substantial supply of propane feedstock required to maintain this
capacity is typically available from propane-rich liquefied petroleum gas
(LPG) streams from gas plant sources. Other processes for the targeted
production of light olefins involve high severity catalytic cracking of
naphtha and other hydrocarbon fractions. A catalytic naphtha cracking
process of commercial importance is described in U.S. Pat. No. 6,867,341.

[0007] More recently, the desire for propylene and other light olefins
from alternative, non-petroleum based feeds has led to the use of
oxygenates such as alcohols and, more particularly, methanol, ethanol,
and higher alcohols or their derivatives. Methanol, in particular, is
useful in a methanol-to-olefin (MTO) conversion process described, for
example, in U.S. Pat. No. 5,914,433. The yield of light olefins from such
processes may be improved using olefin cracking to convert some or all of
the C4.sup.+ product of MTO in an olefin cracking reactor, as
described in U.S. Pat. No. 7,268,265. An oxygenate to light olefins
conversion process in which the yield of propylene is increased through
the use of dimerization of ethylene and metathesis of ethylene and
butylene, both products of the conversion process, is described in U.S.
Pat. No. 7,586,018.

[0008] Despite the use of various dedicated and non-dedicated routes for
generating light olefins industrially, the demand for propylene continues
to outpace the capacity of such conventional processes. Moreover, further
demand growth for propylene is expected. A need therefore exists for
cost-effective methods that can increase propylene yields from both
existing refinery hydrocarbons based on crude oil as well as
non-petroleum derived feed sources.

SUMMARY OF THE INVENTION

[0009] This invention relates to a catalyst for the metathesis of olefins.
Accordingly one embodiment of the invention is a catalyst comprising a
tungsten metal compound characterized in that it contains at least one
tungsten-fluorine bond, the compound dispersed on a refractory oxide
support wherein the compound is chemically bonded to the support.

[0010] These and other objects, embodiments and details of this invention
will become apparent after a detailed description of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0011] As stated, this invention relates to a catalyst for the metathesis
of olefins. The catalyst comprises a tungsten metal compound having at
least one tungsten-fluorine bond which is dispersed on a refractory oxide
support and the compound is chemically bonded to the support.
Accordingly, one necessary component of the invention is a tungsten metal
compound with at least one tungsten-fluorine bond. The tungsten metal
compound has the empirical formula of: WR4F, WOFR3 or
W(NR')FR3, where R is an organic group which does not have any
hydrogen atoms beta to the tungsten, non-limiting examples of which are
neopentyl (--CH2CMe3); methyl, 2,2-diethylpropyl
(--CH2C(CH2CH3)2Me), and 2,2-diethylbutyl
(--CH2C(CH2CH3)2CH2CH3). R' is an organic
group such as but not limited to H, phenyl, 2,6-dimethylphenyl and
methyl. The oxo compound can be synthesized by first reacting
O═WCl4 with an alkylating agent such as RMgCl, RLi, RNa or RK to
give O═WR3Cl which is then reacted with a fluorinating agent
such as AgBF4, HF or NaF to form the O═WR3F compound. The
reaction product is treated with a base to remove BF3 impurities,
such as but not limited to NR''3 where non-limiting examples of R''
include H, methyl, ethyl, and phenyl. The overall process can be
summarized as follows where R is neopentyl and R'' is ethyl.

##STR00001##

[0012] An alternate way to synthesize the oxo tungsten fluoro compound is
to react (O═W--O--W═O) R6 with a fluorinating agent (same as
above) to produce O═WR3F. Synthesis of (O═W--O--W═O)
R6 is described in J. AMER. CHEM. SOC., 1983, vol. 105, 7176-7 which
is incorporated by reference in its entirety.

[0013] To synthesize the imido compound, often the starting
O═WCl4 compound is reacted with R' isocyanate, to yield CO2
and R'N═WCl4 followed by alkylation and fluorination as above.
An example of this synthesis is diagrammatically shown below.

##STR00002##

Alternatively, NH3 can be used in place of R' isocyanate to yield
HN═WCl4 and H2O. As shown in the above equation, if all the
boron is not removed, it can be removed by treatment with silica.

[0014] Having obtained the tungsten-fluorine bond containing compound, it
is now dispersed or grafted onto an inorganic refractory support.
Suitable inorganic refractory supports which can be used include, but are
not limited to, silica, aluminas, silica-alumina, zirconia, titania, etc.
with silica being preferred. Mixtures of refractory oxides can also be
used and fall within the bounds of the invention. The support generally
has a surface area from about 50 to 1000 m2/g, and preferably from
about 80 to about 500 m2/g. It should be pointed out that
silica-alumina is not a physical mixture of silica and alumina but means
an acidic and amorphous material that has been cogelled or
coprecipitated. This term is well known in the art, see e.g., U.S. Pat.
No. 3,909,450, U.S. Pat. No. 3,274,124 and U.S. Pat. No. 4,988,659, all
of which are incorporated by reference in their entirety. Additionally,
naturally occurring silica-aluminas such as attapulgite clay,
montmorillonite clay or kieselguhr are within the definition of
silica-alumina.

[0015] Although the supports can be used as powders, it is preferred to
form the powder into shaped articles. Examples of shaped articles include
but are not limited to spheres, pills, extrudates, irregularly shaped
particles and tablets. Methods of forming these various articles are well
known in the art. The support can also be in the form of a layer on an
inert core such as described in U.S. Pat. No. 6,177,381 which is
incorporated by reference in its entirety.

[0016] Spherical particles may be formed, for example, from the preferred
alumina by: (1) converting the alumina powder into an alumina sol by
reaction with a suitable peptizing acid and water and thereafter dropping
a mixture of the resulting sol and a gelling agent into an oil bath to
form spherical particles of an alumina gel which are easily converted to
a gamma-alumina support by known methods; (2) forming an extrudate from
the powder by established methods and thereafter rolling the extrudate
particles on a spinning disk until spherical particles are formed which
can then be dried and calcined to form the desired particles of spherical
support; and (3) wetting the powder with a suitable peptizing agent and
thereafter rolling the particles of the powder into spherical masses of
the desired size.

[0017] Instead of peptizing an alumina powder, spheres can be prepared as
described in U.S. Pat. No. 2,620,314 which is incorporated by reference
in its entirety. The first step in this method involves forming an
aluminum hydrosol by any of the techniques taught in the art and
preferably by reacting aluminum metal with hydrochloric acid. The
resultant hydrosol is combined with a suitable gelling agent such as
hexamethylene tetraamine (HMT). The resultant, mixture is dropped into an
oil bath which is maintained at a temperature of about 90° to
about 100° C. The droplets of the mixture remain in the oil bath
until they set and form hydrogel spheres. Next the spheres are
continuously withdrawn from the oil, bath and treated with an ammoniacal
solution at a temperature of about 80° to about 95° C. for
a time of about 2 to about 2.5 hours. After treatment with the ammoniacal
solution, the spheres are dried at a temperature of about 80° to
about 150° C. and then calcined at a temperature of about
400° to about 700° C. for a time of about 1 to about 24
hours.

[0018] Extrudates are prepared by mixing the inorganic hydroxide or oxide
with water and suitable peptizing agents such as nitric acid, acetic
acid, etc. until an extrudable dough is formed. The resulting dough is
then extruded through a suitably sized die to form extrudate particles.
The extrudate particles are dried at a temperature of about 150°
to about 200° C. and then calcined at a temperature of about
450° to 800° C. for a period of about 0.5 to about 10 hours
to effect the preferred form of the refractory inorganic oxide.

[0019] A preferred support is silica with amorphous silica being one type
of silica. Examples include Davisil®46, Davisil®636 (W.R. Grace &
Co., Columbia, Md.) and other precipitated silicas. Regardless of the
source, the silica will have a surface area, either as received or after
an optional acid washing step in the catalyst preparation procedure, of
at least about 50 m2/g and preferably from about 80 to about 500
m2/g, and most preferably from about 400 to about 500 m2/g.
Another form of silica which can be used is any of the crystalline
mesoporous silicas which are defined to be virtually pure silica. These
include materials such as MCM-41 and SBA-15. Additional forms of silica
are zeolites which are defined to be virtually pure silica. Zeolites are
crystalline aluminosilicate compositions which are microporous and which
are formed from corner sharing AlO2 and SiO2 tetrahedra. By
virtually pure silica zeolites is meant that virtually all the aluminum
has been removed from the framework. It is well known that it is
virtually impossible to remove all the aluminum. Numerically, a zeolite
is virtually pure silica when the Si/Al ratio has a value of at least
3,000, preferably 10,000 and most preferably 20,000.

[0020] The silica described above can optionally be acid washed (see U.S.
patent application Ser. No. 12/701,508 which is incorporated by reference
in its entirety) to further improve the properties of the resulting
catalyst. Acid washing involves contacting the silica with an acid,
including an organic acid or an inorganic acid. Particular inorganic
acids include nitric acid, sulfuric acid, and hydrochloric acid, with
nitric acid and hydrochloric acid being preferred. The acid concentration
in aqueous solution, used for the acid washing, is generally in the range
from about 0.05 molar (M) to about 3 M, and often from about 0.1 M to
about 1 M. The acid washing can be performed under static conditions
(e.g., batch) or flowing conditions (e.g., once-through, recycle, or with
a combined flow of make-up and recycle solution).

[0021] Representative contacting conditions for acid washing the silica
support include a temperature generally from about 20° C.
(68° F.) to about 120° C. (248° F.), typically from
about 30° C. (86° F.) to about 100° C. (212°
F.), and often from about 50° C. (122° F.) to about
90° C. (194° F.). The contacting time is generally from
about from about 10 minutes to about 5 hours, and often from about 30
minutes to about 3 hours. It has been determined that acid washing
increases the BET surface area of the silica support at least 5% (e.g.,
from about 5% to about 20%), and often at least 10% (e.g., from about 10%
to about 15%). For zeolitic forms of silica, acid washing decreases the
amount of aluminum in the framework, i.e. increases the Si/Al ratio. A
third effect of acid washing is a decrease in the average pore diameter
of the silica support. In general, the pore diameter is decreased by at
least about 5%, and often by at least about 10%.

[0022] The tungsten-fluoro compound is now grafted onto the desired
support by one of several techniques including contacting the support
with a solution containing the tungsten-support, sublimation of the
tungsten compound onto the support and direct contacting of the tungsten
compound with the desired support. When the tungsten compound is
contacted with the support using a solution, the compound is first
dissolved in an appropriate solvent. Solvents which can be used to
dissolve the compound include but are not limited to diethylether,
pentane, benzene, and toluene depending on the R groups and compound
reactivity. Contacting is carried out at a temperature of about
-100° to about 80° C., preferably at a temperature of about
-75° to about 35° C. for a time of about 5 minutes to about
24 hours and preferably for a time from about 15 minutes to about 4
hours. The amount of tungsten-fluoro compound dispersed on the support
can vary widely but is usually from about 0.5 to about 10 wt-% of the
catalyst (support plus compound) as the metal. Preferably the amount of
compound is from about 1.5 to about 7 wt-%.

[0023] For sublimation, the tungsten compound is sublimed under dynamic
vacuum (typically less than 10-3 torr) onto the support by heating
the tungsten compound at a temperature of about 30° to about
150° C. The support is then heated to a temperature of about
30° to about 150° C. for about 1 to 4 hours, and the excess
of the tungsten compound is removed by reverse sublimation at a
temperature of about 30° to about 150° C. and condensed
into a cooled area.

[0024] For the direct contact method of grafting the tungsten compound
onto the support, the tungsten compound and the support are stirred at a
temperature of about -10° to about 100° C. for a time of
about 2 to about 6 hours under an inert atmosphere, e.g. argon. All
volatile compounds are condensed into another reactor. A solvent such as
pentane is then introduced into the reactor by distillation, and the
solid is washed three times with the solvent e.g. pentane via
filtration-condensation cycles. After evaporation of the solvent, the
catalyst powder is dried under vacuum. Without being bound by theory, it
is thought that regardless of the preparation method, hydroxyls on the
support surface react with W--R bond(s) to form W--O-- support bonds,
with concomitant release of RH.

[0025] The catalyst of the invention is useful as a metathesis catalyst.
Olefin metathesis (or disproportionation) processes involve contacting a
hydrocarbon feedstock with the catalyst described above at metathesis
reaction conditions. The hydrocarbon feedstock refers to the total,
combined feed, including any recycle hydrocarbon streams, to the catalyst
in the metathesis reactor or reaction zone, but not including any
non-hydrocarbon gaseous diluents (e.g., nitrogen), which may be added
along with the feed according to some embodiments. The hydrocarbon
feedstock may, but does not necessarily, comprise only hydrocarbons. The
hydrocarbon feedstock generally comprises predominantly (i.e., at least
50% by weight) hydrocarbons, typically comprises at least about 80%
(e.g., from about 80% to about 100%) hydrocarbons, and often comprises at
least about 90% (e.g., from about 90% to about 100% by weight)
hydrocarbons.

[0026] Also, in olefin metathesis processes according to the present
invention, the hydrocarbons contained in the hydrocarbon feedstock are
generally predominantly (i.e., at least 50% by weight, such as from about
60% to about 100% by weight) olefins, typically they comprise at least
about 75% (e.g., from about 75% to about 100%) by weight olefins, and
often they comprise at least about 85% (e.g., from about 85% to about
100% or from about 95% to about 100%) by weight olefins. In other
embodiments, these amounts of olefins are representative of the total
olefin percentages in the hydrocarbon feedstock itself, rather than the
olefin percentages of the hydrocarbons in the hydrocarbon feedstock. In
yet further embodiments, these amounts of olefins are representative of
the total percentage of two particular olefins in the hydrocarbon
feedstock, having differing carbon numbers, which can combine in the
metathesis reactor or reaction zone to produce a third olefin having an
intermediate carbon number (i.e., having a carbon number intermediate to
that of (i) a first olefin (or first olefin reactant) and (ii) a second
olefin (or second olefin reactant) having a carbon number of at least two
greater than that of the first olefin). In general, the two olefins are
present in the hydrocarbon feedstock to the metathesis reactor in a molar
ratio of the first olefin to the second olefin from about 0.2:1 to about
10:1, typically from about 0.5:1 to about 3:1, and often from about 1:1
to about 2:1.

[0027] In an exemplary embodiment, the two olefins (first and second
olefins) of interest are ethylene (having two carbons) and butylene
(having four carbons), which combine in the metathesis reactor or
reaction zone to produce desired propylene (having three carbons). The
term "butylene" is meant to encompass the various isomers of the C4
olefin butene, namely butene-1, cis-butene-2, trans-butene-2, and
isobutene. In the case of metathesis reactions involving butylene, it is
preferred that the butylene comprises predominantly (i.e., greater than
about 50% by weight) butene-2 (both cis and trans isomers) and typically
comprises at least about 85% (e.g., from about 85% to about 100%)
butene-2, as butene-2 is generally more selectively converted, relative
to butene-1 and isobutylene, to the desired product (e.g., propylene) in
the metathesis reactor or reaction zone. In some cases, it may be
desirable to increase the butene-2 content of butylene, for example to
achieve these ranges, by subjecting butylene to isomerization to convert
butene-1 and isobutylene, contained in the butylene, to additional
butene-2. The isomerization may be performed in a reactor that is
separate from the reactor used for olefin metathesis. Alternatively, the
isomerization may be performed in an isomerization reaction zone in the
same reactor that contains an olefin metathesis reaction zone, for
example by incorporating an isomerization catalyst upstream of the olefin
metathesis catalyst or even by combining the two catalysts in a single
catalyst bed. Suitable catalysts for carrying out the desired
isomerization to increase the content of butene-2 in the butylene are
known in the art and include, for example, magnesium oxide containing
isomerization catalysts as described in U.S. Pat. No. 4,217,244.

[0028] As discussed above, the olefins may be derived from petroleum or
non-petroleum sources. Crude oil refining operations yielding olefins,
and particularly butylene, include hydrocarbon cracking processes carried
out in the substantial absence of hydrogen, such as fluid catalytic
cracking (FCC) and resid catalytic cracking (RCC). Olefins such as
ethylene and butylene are recovered in enriched concentrations from known
separations, including fractionation, of the total reactor effluents from
these processes. Another significant source of ethylene is steam
cracking, as discussed above. A stream enriched in ethylene is generally
recovered from an ethylene/ethane splitter as a low boiling fraction,
relative to the feed to the splitter, which fractionates at least some of
the total effluent from the steam cracker and/or other ethylene
containing streams. In the case of olefins derived from non-petroleum
sources, both the ethylene and butylene, for example, may be obtained as
products of an oxygenate to olefins conversion process, and particularly
a methanol to light olefins conversion process. Such processes are known
in the art, as discussed above, and optionally include additional
conversion steps to increase the butylene yield such as by dimerization
of ethylene and/or selective saturation of butadiene, as described in
U.S. Pat. No. 7,568,018. According to various embodiments of the
invention, therefore, at least a portion of the ethylene in the
hydrocarbon feedstock is obtained from a low boiling fraction of an
ethylene/ethane splitter and/or at least a portion of the butylene is
obtained from an oxygenate to olefins conversion process.

[0029] With respect to the first and second olefins (e.g., ethylene and
butylene) that undergo metathesis, the conversion level, based on the
amount of carbon in these reactants that are converted to the desired
product and by-products (e.g., propylene and heavier, C5.sup.+
hydrocarbons), is generally from about 40% to about 80% by weight, and
typically from about 50% to about 75% by weight. Significantly higher
conversion levels, on a "per pass" basis through the metathesis reactor
or reaction zone, are normally difficult to achieve due to equilibrium
limitations, with the maximum conversion depending on the specific olefin
reactants and their concentrations as well as process conditions (e.g.,
temperature).

[0030] In one or more separations (e.g., fractionation) downstream of the
metathesis reactor or reaction zone, the desired product (e.g.,
propylene) may be recovered in substantially pure form by removing and
recovering unconverted olefins (e.g., ethylene and butylene) as well as
reaction by-products (e.g., C5.sup.+ hydrocarbons including olefin
oligomers and alkylbenzenes). Recycling of the unconverted olefin
reactants back to the metathesis reactor or reaction zone may often be
desirable for achieving complete or substantially complete overall
conversion, or at least significantly higher overall conversion (e.g.,
from about 80% to about 100% by weight, or from about 95% to about 100%
by weight) than the equilibrium-limited per pass conversion levels
discussed above. The downstream separation(s) are normally carried out to
achieve a high purity of the desired product, particularly in the case of
propylene. For example, the propylene product typically has a purity of
at least about 99% by volume, and often at least about 99.5% by volume to
meet polymer grade specifications. According to other embodiments, the
propylene purity may be lower, depending on the end use of this product.
For example, a purity of at least about 95% (e.g., in the range from
about 95% to about 99%) by volume may be acceptable for a non-polymer
technology such as acrylonitrile production, or otherwise for
polypropylene production processes that can accommodate a lower purity
propylene.

[0031] At the per pass conversion levels discussed above, the selectivity
of the converted feedstock olefin components (e.g., ethylene and
propylene) to the desired olefin(s) (e.g., propylene) having an
intermediate carbon number is generally at least about 75% (e.g., in the
range from about 75% to about 100%) by weight, typically at least about
80% (e.g., in the range from about 80% to about 99%) by weight, and often
at least about 90% (e.g., in the range from about 90% to about 97%) by
weight, based on the amount of carbon in the converted products. The per
pass yield of the desired olefin(s) is the product of the selectivity to
this/these product(s) and the per pass conversion, which may be within
the ranges discussed above. The overall yield, using separation and
recycle of the unconverted olefin reactants as discussed above, can
approach this/these product selectivity/selectivities, as essentially
complete conversion is obtained (minus some purge and solution losses of
feedstock and product(s), as well as losses due to downstream separation
inefficiencies).

[0032] The conversion and selectivity values discussed above are achieved
by contacting the hydrocarbon feedstock described above, either
continuously or batchwise, with a catalyst as described herein.
Generally, the contacting is performed with the hydrocarbon feedstock
being passed continuously through a fixed bed of the catalyst in an
olefin metathesis reactor or reaction zone. For example, a swing bed
system may be utilized, in which the flowing hydrocarbon feedstock is
periodically re-routed to (i) bypass a bed of catalyst that has become
spent or deactivated and (ii) subsequently contact a bed of fresh
catalyst. A number of other suitable systems for carrying out the
hydrocarbon/feedstock contacting are known in the art, with the optimal
choice depending on the particular feedstock, rate of catalyst
deactivation, and other factors. Such systems include moving bed systems
(e.g., counter-current flow systems, radial flow systems, etc.) and
fluidized bed systems, any of which may be integrated with continuous
catalyst regeneration, as is known in the art.

[0033] Representative conditions for olefin metathesis (i.e., conditions
for contacting the hydrocarbon feedstock and catalyst in the olefin
metathesis reactor or reaction zone), in which the above conversion and
selectivity levels may be obtained, include a temperature from about
75° C. (572° F.) to about 600° C. (1112° F.),
and often from about 100° C. (752° F.) to about 500°
C. (932° F.); a pressure from about 50 kPa gauge (7.3 psig) to
about 8,000 kPa gauge (1160 psig), and often from about 1,500 kPa gauge
(218 psig) to about 4,500 KPa gauge (653 psig); and a weight hourly space
velocity (WHSV) from about 1 hr-1 to about 10 hr-1. As is
understood in the art, the WHSV is the weight flow of the hydrocarbon
feedstock divided by the weight of the catalyst bed and represents the
equivalent catalyst bed weights of feed processed every hour. The WHSV is
related to the inverse of the reactor residence time. Under the olefin
metathesis conditions described above, the hydrocarbon feedstock is
normally in the vapor phase in the olefin metathesis reactor or reaction
zone, but it may also be in the liquid phase, for example, in the case of
heavier (higher carbon number) olefin feedstocks.

[0034] The following examples are set forth to illustrate the invention.
It is to be understood that the examples are only by way of illustration
and are not intended as an undue limitation on the broad scope of the
invention as set forth in the appended claims.

[0035] All experiments were carried out using standard Schlenk and
glove-box techniques. Solvents were purified and dried according to
standard procedures. SiO2-(700) was prepared from Aerosil® silica
from Degussa (specific area of 200 m2/g), by partial dehydroxylation
at 700° C. under high vacuum (10-5 Torr) for 15 h to give a
white solid having a specific surface area of 190 m2/g and
containing 0.7 OH nm-2.

Example 1

Synthesis of W═OF(CH2CMe3)3

[0036] The synthesis of [W═O(CH2CMe3)3F] was carried
out according to the following reaction.

##STR00003##

W═O(CH2CMe3)3Cl was synthesized by the literature
procedure (Schrock et.al., J. Am. CHEM. SOC. 1984, 106, 6305-10).
[W═O(CH2CMe3)3Cl] (1.5 g, and AgBF4 (0.65 g) were
stirred in 20 mL of toluene for one hour at room temperature. The
reaction mixture was filtered to remove the insoluble AgCl, and NEt3
(1.1 mL) was added to remove the BF3 moiety by precipitation as
BF3.N(C2H5)3. The resulting solution was stirred for
16 h at room temperature and then filtered over celite. The solvent was
then removed under vacuum to provide a white solid which was sublimed at
60° C. under reduced pressure (3.10-5 Torr) to yield 1.13 g of
product. The product was analyzed and found to contain 41.47% C, 7.89% H
and 4.72% F which agrees well with calculated percentages for
C15H33OFW of 41.69% C, 7.69% H and 4.42% F.

Example 2

Synthesis of W(NPh)F(CH2CMe3)3

[0037] W(NPh)F(CH2CMe3)3 was synthesized by reaction of
WOCl4 with C6H5NCO, followed by alkylation with neopentyl
magnesium chloride as shown below.

##STR00004##

Freshly distilled phenylisocyanate (3.214 g) was added to a suspension of
[W═OCl4] (9.000 g) in 200 mL of heptane. This mixture was heated
at reflux temperature for 4 days to provide a dark brown precipitate. The
solvent was removed under vacuum and Et2O (20 mL) was added
resulting in a green solution mixture which was filtered to remove the
insoluble impurities and Et2O was then removed under vacuum
producing a powder of dark green crystals of
[W═N(C6H5)Cl4].(Et2O). A solution of 10.6 g
[W═N(C6H5)Cl4].(Et2O) in toluene was prepared and
stirred rapidly. This solution was cooled to -78° C. and to it
there were added (dropwise) 30 mL of a 2.17 M ether solution of
neopentylmagnesium chloride. The mixture was warmed up slowly to room
temperature with continuous stirring at which point the solvent was
removed under vacuum. The resulting product was extracted with pentane,
and the extract was treated with activated carbon, stirred for 30
minutes, filtered through a bed of celite, and then the solvent was
removed under vacuum. The yellow brown residue was collected on a frit,
washed with chilled pentane and dried to give 3.8 g of
[W═N(C6H5)(CH2CMe3)3Cl] as a brown powder.

[0038] A portion of the
[W═N(C6H5)(CH2CMe3)3Cl] (2.000 g) obtained
above and 0.74 g of AgBF4 were stirred in 20 mL of toluene for one
hour at room temperature. The reaction mixture was filtered to remove the
insoluble AgCl, and 1.1 mL of NEt3 was added. The resulting solution
was stirred for 16 h at room temperature, filtered over celite and the
solvent then removed under vacuum to provide a yellow pale solid. The
product still contained boron as observed by 11B NMR. A solution of
the product in pentane was added to SiO2-(700) (500 mg) and reacted
for 4 hours. The silica was extracted 3 times with pentane, the solutions
combined and the solvent was then removed under vacuum to provide a
yellow pale solid. This product was sublimed at 60° C. under
reduced pressure (3×105 Torr) to yield 580 mg of pure product.
The product was analyzed and found to contain 48.86% C, 7.38% H, 4.54% F;
2.74% N and 34.90% W which agrees well with calculated percentages for
C21H38FNW of 49.71% C, 7.55% H, 3.74% F; 2.76% N and 36.23% W.

Example 3

Synthesis of WOF(CH2CMe3)3/SiO2

[0039] A mixture of the product of Example 1
[WO(CH2CMe3)3F] (500 mg) in pentane (10 mL) and
SiO2-(700) (2 g) was stirred at 25° C. overnight. After
filtration, the solid was washed 5 times with pentane and all volatile
compounds were condensed into another reactor (of known volume) in order
to quantify neopentane evolved during grafting. The resulting white
powder was dried under vacuum (10-5 Torr). Analysis by gas
chromatography indicated the formation of 290 μmol of neopentane
during the grafting (1.0±0.1 NpH/W). Elemental analysis showed: W 4.43
wt-%; C 3.27 wt-%.

Catalytic Testing in Propylene Metathesis of the Catalyst of Example 3

[0041] A stainless-steel half-inch cylindrical reactor that can be
isolated from ambient atmosphere was charged with 128 mg of the catalyst
of Example 3 in a glovebox. After connection to the gas lines and purging
of the tubing, a 20 ml/min flow of purified propylene was passed over the
catalyst bed at 80° C. Hydrocarbon products were analyzed online
by GC. At 30 hours on stream, the catalyst exhibited a total turn over
number of 8300. Selectivity was 50% to ethylene and 50% to 2-butenes. The
E/Z ratio of the 2-butene formed was 1.5.

Example 6

Catalytic Testing in Propylene Metathesis of the Catalyst of Example 4

[0042] A stainless-steel half-inch cylindrical reactor that can be
isolated from ambient atmosphere was charged with 135 mg of the catalyst
of Example 4 in a glovebox. After connection to the gas lines and purging
of the tubing, a 20 ml/min flow of purified propylene was passed over the
catalyst bed at 80° C. Hydrocarbon products were analyzed online
by GC. At 30 hours on stream, the catalyst exhibited a total turn over
number of 1150. Selectivity was 50% to ethylene and 50% to 2-butenes. The
E/Z ratio of the 2-butene formed was 0.9.

Patent applications by Christopher P. Nicholas, Evanston, IL US

Patent applications by Etienne Mazoyer, Lyon FR

Patent applications by Jean-Marie Basset, Caluire FR

Patent applications by Mostafa Taoufik, Villeurbanne FR

Patent applications by UOP LLC

Patent applications in class Including phosphorus or sulfur or compound containing nitrogen or phosphorus or sulfur

Patent applications in all subclasses Including phosphorus or sulfur or compound containing nitrogen or phosphorus or sulfur